an intricate knot tied by Gordius, the king of Phrygia, and cut by the sword of Alexander the Great after he heard that whoever undid it would become ruler of Asia
any very difficult problem; insoluble in its own terms
any of various small animals or insects that are pests; e.g. cockroaches or rats; "cereals must be protected from mice and other vermin"; "he examined the child's head for vermin"; "boys in the village have probably been shooting vermin"